Quantitative assay of lentinan in human blood with the limulus colorimetric test

A conventional limulus test detects not only endotoxin but also beta (1----3) glucan. Therefore, using a quantitative limulus test (the limulus colorimetric test) we studied the pharmacokinetics of lentinan, an antitumor beta (1----3) glucan, in the blood of 10 health volunteers and three patients with advanced gastric cancer. The calibration curve of lentinan in the human plasma was linear in the range of 0 to 100 ng/ml. When incubated with human plasma at 37 degrees C in vitro, lentinan had the recovery of almost 100% as compared to the initial concentration even after 60-min incubation, indicating the stability of lentinan in human plasma. When 1 mg of lentinan was intravenously administered over a 2 hr period, lentinan concentration reached the maximum levels (50-80 ng/ml) at the end of the drip infusion and decreased gradually thereafter. In the near future, the more appropriate modes of lentinan administration will be determined by further investigation of its kinetics in the human body.